As an after-treatment device for a diesel engine, which is configured to minimize contaminants and preserve atmospheric environment, a catalyzed particulate filter including a diesel oxidation catalyst (hereinafter referred to as “DOC”) and a diesel particulate filter (hereinafter referred to as “DPF”) is widely used in the art.
The purification of diesel engine exhaust gas is mainly aimed at reducing nitrogen oxides (NOx) and particulate materials (PM, various harmful particulate materials including exhaust gas), and these materials are adsorbed on the DOC or by the DPF during the exhaust process. When the nitrogen oxides and particulate materials are continuously accumulated, the processing performance of the device is reduced, and thus periodic regeneration is required.
In the exhaust gas after-treatment device, the regeneration is mainly achieved by increasing the engine RP to increase the exhaust gas temperature or operating a separate regeneration device to heat and burn the particulate materials adsorbed/collected in the device to be removed, and the regeneration time is determined depending on the amount of collected particulates detected by a differential pressure sensor or depending on a predetermined cycle stored in an ECU when the amount of adsorbed/collected particulates increases or when the predetermined cycle has elapsed.
In order to achieve more effective purification treatment in the above-described exhaust gas after-treatment device and to achieve more effective regeneration in reprocessing of the particulate materials collected by the DPF, it is important for the exhaust gas introduced into the exhaust gas after-treatment device to have flow characteristics with uniform distribution over the entire area of the DOC.
However, in the case of a typical exhaust gas after-treatment device mounted in a conventional agricultural vehicle, the flow of exhaust gas is generally not uniform over the entire area of the DOC and is concentrated in a local area. As a result, the catalysis efficiency of the DOC is reduced, and the particulate materials are locally accumulated in the DPF, which are problematic.
Furthermore, when the particulate materials are locally accumulated in the DPF due to the non-uniform flow of exhaust gas, heat exceeding a heat resistance limit of the DPF is instantaneously generated as the locally accumulated particulate materials are burned during the regeneration of the DPF, which makes the DPF unusable, and thus the DPF should be replaced with a new one.